Fluorocarbons oxidative degradation

The by-products formed are shorter-chain sulfonyl fluorides or chlorides and fluorocarbons [51-54]. The structures of the by-products suggest a cleavage of carbon-sulfur and carbon-carbon bonds and some oxidative degradation as well. 

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

It should not be thought, however, that perfluorocarbons are completely inert toward combustion. Even the very inert perfluorocarbon polymer polytetrafluoroethylene [PTFE, Du Pont s Teflon F(CF2CF2)nF] is thermodynamically unstable in oxygen with respect to CO2 and CF4 (Exercise 12.6) and can burn in a 95% 02/5% N2 mixture at 0.1 MPa, although combustion is hard to initiate because of the nonvolatility of PTFE and the resistance of the thermal degradation products to oxidation. Conflagrations involving more reactive, volatile fluorocarbons such as perfluoro-toluene have been reported.15... 

Although the technological basis of all fluorine-containing plastics and most elastomers continues to be the free radical polymerization of fluoroolefins, which themselves are based on the vastly greater fluorocarbon refrigerant industry, important advances have been made in the past two decades These include primarily the production of polymers that are more resistant to degradation by heat, oxidation, bases, and solvents, as well as polymers that are more easily processable, that is, able to be converted mto their final forms for use, whether by thermoplastic or thermoset processes [1,2,3,4]... 

Aromatic molecules with fluorine or fluorine-containing substituents frequently have high bioactivity [39] and are therefore used for medical and agrochemical applications, in which they are deliberately introduced to organisms and/or the environment (Fig. 2). They are typically less bioaccumulative and less environmentally persistent than saturated fluorocarbons, and may be degraded oxidatively under aerobic conditions, where defluorination may or may not occur.5 The world market for fluoroaromatics was estimated at 10,000 tonne per annum in... 

Fluorine contamination has been reported in various environments and applications in the past. It has shown up in plasma processing [10-18], as crosscontamination from storage in contaminated containers or with contaminated samples [14,18], and modification of aluminum deposited on fluoropolymer substrates and other polymers having fluorine-based plasma treatments has also been observed [19-21]. Fluorocarbon lubricants have also been noted to modify the oxide structures on aluminum alloys [22,23], and the degradation of AI2O3 catalytic supports has been associated with fluoride conversion during reactions with fluorocarbons [24]. Alloy oxide modification has also been well noted in the presence of fluorine compounds not of the fluorocarbon family [25]. 

The global presence of radioactive fallout from the nuclear bomb tests of the 1950s and 1960s clearly illustrated the capacity of the atmosphere to distribute chemicals around Earth. Global transport has been demonstrated for a large number of chemicals that do not rapidly degrade or settle out of the atmosphere. Examples are methane (CH4), nitrous oxide (N20), and chloro-fluorocarbons (CFCs), all of which have half-lives in the atmosphere ranging from years to decades. 

Many polymeric materials serve in applications that require exposure to outdoor conditions. Any resultant degradation is termed weathering, which may be a combination of several different processes. Under these conditions, deterioration is primarily a result of oxidation, which is initiated by ultraviolet radiation from the sun. Some polymers, such as nylon and cellulose, are also susceptible to water absorption, which produces a reduction in their hardness and stiffness. Resistance to weathering among the various polymers is quite diverse. The fluorocarbons are virtually inert under these conditions some materials, however, including poly(vinyl chloride) and polystyrene, are susceptible to weathering. 

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